Gears not working and YouTube hasn’t helped!

By now you have probably viewed several YouTube videos and still can’t seem to get your gears working just right. It is a very simple process when it works but when it doesn’t this guide will help you to  identify the problem.

Let’s start at the very beginning and run through each of the gears including the various combinations possible between the front and back. Unless of course you only have a single chainring up front.  Start in the largest chainring and smallest rear sprocket and operate the gear lever. It doesn’t matter if you are using a road bike, MTB, hybrid. Almost without exception they all work the same way.

Operating the lever should feel smooth with a light action. If it feels stiff it could be an indication of a cable issue but we will come back to that later. Each click of the lever should move the chain promptly, without lag,  to the next largest cog. Once the next gear has been selected the chain should be quiet without any rattles, skips or jumps. If all is good so far keep going through each of the gears until it reaches the largest sprocket and then back down again. Is everything working ok?  Well maybe not as you wouldn’t otherwise be reading this. Going to a larger sprocket requires increased tension on the cable and moving to a smaller sprocket relies upon the gear lever releasing just the right mount of tension so that the cable can slide through its housing.

If you find that most gears work properly but only one or two are making a noise then it is quite likely that the indexing only needs a slight adjustment. Ignoring the smallest and largest sprockets for the moment if the chain rattles in one of the middle gears the cable could either be too tight or too loose. When in that noisy gear I like to push the derailleur by hand ever so slightly replicating the movement it makes when the gear lever is operated. If pushing it quietens it down then you know that the cable isn’t quite tight enough. If pushing it slightly does nothing or makes it worse try pulling it slightly. If that approach quietens the chain then the cable needs to be loosened slightly.

Adjusting the tension is very straightforward and is carried out by a barrel adjuster at the point that the cable enters the rear derailleur or at the point that the cable enters the gear lever on the handlebar (common on hybrids and mountain bikes). Regardless of where your barrel adjuster is turning it anti clockwise will tighten the cable and turning it in the opposite direction will loosen the cable. Try turning it by half a turn and run through the gears again and see what happens. It should now run quietly. Repeat the whole process in both chainrings and all gears.

If you have found that by tightening the cable all the gears  work when moving from the smallest to the largest sprocket but they do not work well or are reluctant to change in the opposite direction, read on! Moving to a smaller sprocket requires the cable to run smoothly through its housing with as little friction as possible. If the cable is old or showing signs of corrosion then it is likely that a new cable will solve the issue. As they are cheap it is a great place to start. If you haven’t changed a cable in a long time or have ridden it in all weathers for the last year I would highly recommend changing the outer housing as well as the inner cable.

Let’s talk screws for a moment. Rear derailleurs typically have three screws that can be adjusted. A low and high limit screw and another that alters the position of the derailleur called a ‘B’ screw. The limit screws rarely if ever need to be touched if they have been set correctly in the first place. Despite what many bike owners seem to think the limit screws do not adjust indexing. They can impede selection of the smallest or largest sprocket but that is about it.  Their function as the name suggests is to limit the movement of the rear derailleur. The ‘High’ or ‘H’ limit screw stops the derailleur over shifting the chain on the largest sprocket which could cause the chain to go into the spokes. If you are unlucky the derailleur will follow the chain into the spokes potentially damaging itself and the spokes. That is what those clear plastic disks between the cassette and the wheel are designed to stop but don’t. The ‘Low’ or ‘L’ screw, as you might expect does the opposite. In this case it stops the chain falling off of the smallest sprocket which often causes the chain to get jammed between the sprocket and the frame.

If the chain runs smoothly on the smallest sprocket or for that matter doesn’t the first thing to do is to release the tension on the cable by turning the barrel adjuster fully clockwise. This ensures that the cable is not interfering with the limit screw. Turn the limit screw (‘H’) clockwise until the chain starts to rattle then turn it in the opposite direction until the chain starts to rattle. Count the number of turns,  from one extreme to the other, as the correct position will be roughly in the middle. Once set,  back it off half a turn to allow the derailleur to over shift slightly.  Setting the ‘L’ limit screw is a very similar process. Change to the easiest or largest sprocket. Push the derailleur in by hand slowly (towards the spokes). The screw should limit its movement and prevent the chain from falling off into the spokes. While pushing the derailleur in,  loosen the limit screw (anticlockwise) until the chain starts to rattle then tighten by half a turn. If when trying to select the largest sprocket the chain doesn’t quite make the jump or does engage but then falls back to the next sprocket that is an indication that the limit screw needs to be loosened slightly. It could also mean that the cable requires a little more tension but if it is pushing against the limit screw it won’t go any further regardless of how tight the cable is.

Other problems. The ‘B’ screw is very important for smooth shifting, particularly with the largest sprockets. Adjusting the screw will impact chain tension  but that is the subject of another discussion. In the case of indexing, it is used to adjust the position of the upper jockey wheel. Change gears so that the chain is on the largest rear sprocket and smallest front sprocket. The gap between the upper jockey wheel and the cassette should be as close as possible but not so close that the jockey wheel or chain rubs against the cassette. This is an often overlooked adjustment that can make a significant difference to shift performance.

By now everything should be setup and working smoothly. However, if you have changed cables, indexed the gears, adjusted the various screws and it still wont work properly there are a few options. Most of these involve straightening something. The most common thing to bend is the gear hanger (fitted to most bikes but often not on children’s or basic models). The gear hanger is a small vertical plate that sits between the rear derailleur and the frame. It is designed to bend and by doing so protects the frame from damage. They are usually made from a soft alloy and as such bend easily. A good indication of a bent hanger is a bike that suddenly stopped working well coupled with a gouge or scratch on the outside edge of the derailleur. This can easily occur if the bike is dropped or put in the boot of a car derailleur side down. Unfortunately, it is almost impossible to straighten accurately without a specialist tool though they are easily replaceable.

Finally, if none of this works then please ask for advice, we would be very happy to help. Almost forgot, a very worn chain can also impact smooth shifting.